Glufosinate, or 2-amino-4-(hydroxymethyl phosphinyl) butanoic acid and its salts, in particular its monoammonium salt, is represented by the following formula: 
These compounds are selective herbicides, generally used on corn and soybeans resistant to the active ingredient. It is a water-soluble herbicide intended for foliar spray application for the control of a broad spectrum of emerged annual and perennial grass and broadleaf weeds in corn and soybeans. The herbicide is commercially available from AgrEvo USA under the designation xe2x80x9cLIBERTYxe2x80x9d, and is disclosed in U.S. Pat. No. 4,168,963, the disclosure of which is hereby incorporated by reference.
Adjuvants are typically used in formulations to aid the operation or improve the effectiveness of the pesticide, herbicide, etc. The term includes wetting agents, spreaders, emulsifiers, dispersing agents, foaming adjuvants, foam suppressants, penetrants, and correctives. For example, adjuvants such as Valent X-77(copyright) Spreader are commonly used to enhance the performance of Fluazifop-P-butyl, another selective herbicide. However, Valent X-77(copyright) Spreader and other ethoxylated nonionic surfactants contain free ethylene oxide which may form 1, 4 dioxane, a known carcinogen.
To be effective, glufonsinate must be formulated with a high concentration of surfactant, generally about 110 parts surfactant (such as a tallow amine ethoxylate) to 100 parts of glufosinate active ingredient. Indeed, formulation problems with glufosinate are well known, such as those disclosed in U.S. Pat. No. 4,400,196, the disclosure of which is incorporated by reference. In addition to the cost associated with high concentrations of surfactant, such a high surfactant concentration can cause burning at the axils of the corn leaves under certain conditions.
It is therefore an object of the present invention to provide glufosinate adjuvants and formulations which do not suffer from the drawbacks of the prior art.
It is a further object of the present invention to provide glufosinate formulations with increased activity, lower irritancy and lower toxicity than conventional formulations.
It is yet another object of the present invention to provide glufosinate formulations with relatively low amounts of surfactant compared to conventional formulations.
The problems of the prior art have been overcome by the present invention, which provides an adjuvant for glufosinate having excellent activity, lower irritancy and lower aquatic toxicity than conventional adjuvants, as well as the resulting formulation. The adjuvant is C8 to C22 sarcosinate or sarcosinate salt, such as sodium cocoyl sarcosinate, sodium lauroyl sarcosinate, the isopropylamine salt of oleoyl sarcosinate, the isopropylamine salt of cocoyl sarcosinate, or combinations thereof, which is combined with glufosinate and provides effective activity at lower concentrations than conventional formulations. The invention also relates to methods of applying effective amounts of the formulation.
N-Acyl sarcosinates are mild biodegradable surfactants derived from fatty acid and sarcosine. Typically, sarcosinates are used in the form of their sodium, potassium, ammonium or isopropylamnine salt solution. N-Acyl sarcosinates are produced commercially by the Schotten-Baumann reaction of the sodium salt of sarcosine with the appropriate fatty acid chloride under carefully controlled conditions: 
where R is typically a fatty acid of chain length C10 to C18, commonly made from lauric, coconut, palmitic, myristic or oleic acid. After the reaction is complete, the crude sodium salt is acidified to liberate the free fatty sarcosinic acid which is separated from the aqueous by-products. It then is neutralized to a salt form. Sarcosinates such as sodium lauroyl sarcosinate, sodium cocoyl sarcosinate and sodium myristoyl sarcosinate are commercially available under the trademark HAMPOSYL(copyright) from Hampshire Chemical Corp., as 30% active solutions in water.
The present inventors have found that C8 to C22 N-acyl sarcosinates, and in particular, the sodium and isopropylamine salts of cocoyl, oleoyl and lauroyl sarcosinate, are excellent adjuvants for glufosinate, in particular, ammonium glufosinate. The sarcosinates are low in toxicity, including aquatic toxicity, low in irritancy, including ocular irritancy, and when combined with glufosinate at relatively low concentrations, result in formulations that exhibit excellent activity with little or no phytotoxicity.
Suitable salts of these sarcosinates that are useful in the present invention include monoethylamine; diethylamine; triethylamine; alkali metal, particularly sodium and potassium, most preferably sodium; isopropylamine; and ammonia or amino alcohols such as tris amino or 2-dimethylamino-2-methyl-1-propanol. A combination of these salts can be used in a glufosinate formulation.
Preferably 30% sarcosinate solutions are used so that the final concentration of sarcosinate in the formulation is from about 4 to about 40 parts of sarcosinate per 100 parts of glufosinate. Higher concentrations can be used, but concentrations within the aforementioned range are preferred in view of the lower overall cost involved and in view of the desire to minimize phytotoxicity. Concentration of from about 4 to about 16 parts of sarcosinate per 100 parts glufosinate are especially preferred for these reasons. The extremely low amounts of sarcosinate concentrations effective as adjuvants for glufosinate is surprising, in view of the conventional wisdom that high concentrations of surfactant are required in order to obtain effective levels of permeation of glufosinate into the plants, for example.
The aqueous formulations can be prepared by first mixing the appropriate sarcosinate with water, and then mixing the glufosinate herbicide with the resulting surfactant solution.
Preferably the formulations of the present invention are applied as foliar spray directly to the plant or to the locus thereof. Thorough coverage is preferred. Preferably the plant is corn or soybean resistant to glufosinate. Application may be in accordance with conventional teachings. For example, in the case of corn, application may be made from emergence of the crop until the corn is 24xe2x80x3 tall or in the V-7 stage of growth, i.e., 7 developed collars, whichever occurs first. In the case of soybeans, application may be made from emergence to the bloom growth stage. Application is preferably made when weeds are actively growing.